/me wonders if you were booting with media that had an earlier release than the mini accepts

Did you try doing it with the mini's original install? or if the mini came with 10.3, have you tried a 10.4 disc?

I am figuring it loaded from Leopard because it was later than the install that originally came with the disc.

What system is the mini (specs) and what OS X Version did you try to load that you were having issues with?